Among network configurations for interconnecting information terminals, network configurations including wireless communication apparatuses are utilized not only for conventional data transmission for personal computers, but also now incorporated into various home electrical products and utilized for audio and visual transmission, because of advantages as compared with wired communication, e.g., high portability and free installation of terminals, and weight reduction by eliminating wire cables. However, while wireless communication apparatuses have the above advantages, since the wireless communication apparatuses establish communication by emitting electromagnetic waves in a space, the transmission characteristics often degrade in a space provided with many reflectors, due to influence of fading of radio waves arriving after reflections by some objects (delayed waves). In order to reduce this influence, there is a method of controlling the directivity of a transmitting and receiving antenna in response to a radio wave propagation environment.
Conventionally, as countermeasures against fading, there have been proposed methods, such as a method for controlling the directivity of a transmitting and receiving antenna, and a method for controlling various diversity processes. For example, each of Patent Literatures 1 to 3 discloses a directional pattern determining method according to the prior art, involving reception of radio signals in response to changes of a radio wave propagation environment over time.
The invention of Patent Literature 4 is also a directional pattern determining method according to the prior art, involving reception of radio signals in response to changes of a radio wave propagation environment over time. According to this invention, a memory stores, in advance, data for producing a plurality of different directional patterns. These directional patterns are classified into two types: i.e., a weak electric field group consisting of directional patterns each having a relatively wide beam width, and a strong electric field group consisting of directional patterns each having a relatively narrow beam width. At first, one of the groups is selected based on a range of a first parameter measured (e.g., a received signal strength indicator; hereinafter, referred to as RSSI). Next, an optimum directional pattern is determined based on a second parameter measured while sequentially setting the directional patterns of the selected group (e.g., a signal power to noise power ratio; hereinafter, referred to as SNR).
Citation List
Patent Literature
PATENT LITERATURE 1: Japanese Patent Laid-open Publication No. 2000-134023.
PATENT LITERATURE 2: Japanese Patent Laid-open Publication No. 2005-142866.
PATENT LITERATURE 3: Japanese Patent Laid-open Publication No. H08-172423.
PATENT LITERATURE 4: PCT International Publication No. WO2009/144930.